This application claims priority under 35 U.S.C. xc2xa7xc2xa7119 and/or 365 to patent application Ser. No. 100 38 066.2 filed in Germany on Aug. 4, 2001, the entire content of which is hereby incorporated by reference.
The invention concerns an activatable battery for an electronic artillery fuse of the type comprising an ampoule filled with electrolyte and an activation device for rupturing the ampoule in response to the launching of an artillery shell carrying the fuse.
Such a battery of lithium-thionyl chloride type with a plurality of cells is known for example from German Document 37 18 788-A1. That known battery includes a container in which is disposed a rupturable vessel or ampoule which is filled with electrolyte. Also within the container is a stack of inert metal discs or plates which have a lithium layer on one surface and a layer of bound carbon black on the other surface. The metal plates or discs which are coated in that way are separated from each other by separators and form the pile of the multi-cell battery. The pile is contacted with electrodes. Disposed outside the container is a kinetic weight which functions as an inertia body and is so dimensioned that it ruptures the ampoule when a given level of acceleration is applied.
Electronic artillery fuses involve the use of activatable batteries of that kind, which in general are activated by the acceleration occurring upon launch of a projectile provided with the artillery fuse. The ruputable ampoule in the battery is associated with an activation device in the form of for example, an inertia body (kinetic weight) and which is restrained against initial movement by, for example, a spring element or a tear-away cross-piece. Activation of the battery is triggered by virtue of the fact that, when a defined level of acceleration is reached, the resulting impulse acting on the fuse causes the preset spring force of the spring element to be exceeded (or the tear-away cross-piece tears away). Upon such activation occurring, the ampoule immediately impacts against an abutment (formed for example by the bottom of the battery) and ruptures, with the electrolyte in the ampoule being released. The electrolyte then penetrates into the cells of the battery whereafter the battery supplies an electrical voltage.
Those simple triggering mechanisms of the activation device which rely solely upon a spring element or a tear-away cross-piece to control the movement are thus dependent on the magnitude of the force (impulse) acting on the fuse, i.e., the design is force magnitude-dependent. Typically, the design is such that the triggering of the battery occurs as soon as the impulse acting on a projectile reaches a certain magnitude, which magnitude is intended to equal the minimum acceleration level available in the launch barrel (in order to achieve a high level of triggering reliability). For safety reasons, that magnitude should be far greater than any possible non-launch impulses that can be applied to the battery such as unwanted shocks or impacts which occur when handling the fuses or projectiles.
In new modern weapon systems, more specifically in the case of artillery, the loadings applied to the battery during handling and automatic feed into the ammunition store have increased. On the other hand, due to the increased-length barrels, the minimum launch accelerations available therein have further decreased. Those two aspects, that is to say the increased non-launch loadings, and the reduction in the minimum available launch acceleration conflict with each other in relation to the activation level which is to be set for the batteries. In the case of new modern weapon systems, it is not impossible for the minimum available launch acceleration to be at a lower level than that occurring when a fuse is accidentally dropped freely from the normal handling height. As is readily clear, the result of this is that, upon such unwanted handling loadings or in the event of the fuse falling freely from the handling height, the battery is undesirably prematurely activated and as a result the fuse is then no longer operational.
In consideration of those factors, an object of the present invention is to provide an activatable battery of the kind set forth in the opening part of this specification, with reliable free-fall safety.
In accordance with the invention, that object is attained by a battery for an electronic artillery fuse. The battery is activated in response to the release of electrolyte contained in the battery. The battery comprises a rupturable ampoule containing the electrolyte. The ampoule is rupturable in response to contact with a rupturing surface of the battery. The ampoule is normally held in mutually spaced relationship to the rupturing surface. A restraining member is provided which applies a yieldable restraining force for opposing inertia applied to the fuse to maintain the mutually spaced relationship. The restraining force is yieldable against inertia greater than a predetermined value to permit the ampoule and the rupturing surface to approach one another. A timing device is provided for increasing a time period that the inertia of predetermined value must be applied in order for the ampoule and the rupturing surface to contact one another.
By virtue of the fact that, in accordance with the invention, the activation device which is provided to rupture the ampoule which is filled with the electrolyte has a timing member which is provided to evaluate the duration of the shock force respectively acting on the battery, that is to say the impulse, it is possible for the acceleration profile of an unwanted shock or impact upon handling or in the event of a free fall from the handling height to be clearly distinguished from launch acceleration in the barrel. In the event of a free fall onto hard ground the duration of the impulse is in the xcexcsec range. In the event of launch from a barrel the impulse duration is in the msec range. By means of the activatable battery according to the invention, the problem of known activatable batteries which utilise only the impulse magnitude, that is to say the impulse amplitude, can be resolved by virtue of the fact that the activation device which hitherto evaluates only the magnitude of the acceleration is replaced by an activation device which evaluates the impulse duration. Loadings involved in handling, for example due to unwanted shocks or impacts, in the automatic feed into the ammunition store or when a fuse is allowed to fall free with the battery fitted thereto, from the handling height, are not relevant in relation to the activatable battery according to the invention, that is to say they do not result in failure of the battery.
The small compact structure of the overall arrangement which is inexpensive to produce is an advantage. Impulse safety is therefore not susceptible to trouble, within the battery housing, in the event of external influences acting thereon.